In the case where a user captures an image of a subject with a camera, the captured image may have blur. This blur appearing on an image is roughly classified into two types, hand shake blur and motion blur. The hand shake blur indicates blur which is due to camera shake at the moment of pressing the shutter. The motion blur indicates blur which is due to movement of the subject while being photographed.
Characteristics of such hand shake blur and motion blur are represented by a point spread function (hereinafter referred to as PSF). The PSF indicates a function which shows the intensity distribution of a blurred or out-of-focus point image. FIGS. 14A and 14B illustrate the PSF. For example, as shown in FIG. 14A, an image 1003 represents a PSF which indicates deterioration from a focused image 1001 to an out-of-focus image 1002. Furthermore, as shown in FIG. 14B, an image 1006 represents a PSF which indicates deterioration from an unblurred image 1004 to an image 1005 that is blurred in the x direction.
By the way, in recent years, techniques for correcting hand shake blur (for example, electronic hand-shake blur correction and optical hand-shake blur correction) have been put into practice. Specifically, in the case of the optical hand-shake blur correction, hand movement at the time of shooting is estimated based on information from a sensor such as a gyroscope, for example. According to the estimated movement, a lens mechanism or a light-receiving unit sensor is then controlled to correct hand shake blur. In the case of the electronic hand-shake blur correction, a PSF is calculated based on information from a sensor such as a gyroscope, for example. The calculated PSF is then used to correct an image, thereby correcting hand shake blur. The PSF for hand shake blur corresponds to hand movement at the time of shooting and therefore is almost uniform in a whole image.
On the other hand, the PSF for motion blur corresponds to subject movement and therefore is often different from one region to another of an image. It is therefore difficult to correct motion blur in the same method as that used to correct hand shake blur.
In response to this, as a technique for correcting motion blur, a method has been proposed which uses a sequence of images with low resolutions captured using a high-speed shutter and an image with a high resolution captured using a low-speed shutter (refer to Non-Patent Literature 1, for example). In the method disclosed by the Non-Patent Literature 1, a movement of subject image is estimated by correlating pixels with each other among multiple images included in a sequence of low-resolution images with less blur captured using a high-speed shutter. Using the estimated movement of subject image, an image with more blur captured using a low-speed shutter is then corrected so that a high-resolution image with motion blur corrected is obtained.
As another technique for correcting motion blur, a method has been proposed which uses multiple images consecutively captured (refer to Patent Literature 1, for example). In the method disclosed by the Patent Literature 1, as in the method disclosed by the Non-Patent Literature 1, a movement (trajectory) of the subject is obtained based on multiple images consecutively captured, to thereby obtain one degradation function (for example, PSF) which indicates degradation characteristics at all the pixel positions of a target image. Using the degradation function thus calculated, an unblurred image is generated from the target image.